phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('bca423c9ccfb104fa09fd58bc409b7e8', -1, 1368968935, 1368968935, '6b1481d4', 3, 0, 0)

Line : 187
File : sessions.php